Cooling system



COOLING SYSTEM Filed Aug. 22, 1938 5 Sheets-Sheet l 46 Q 48 as I 8 1&4. r

ife/5km 1 g July 23, 1940. F. w. JAHN 2,208,984

COOLING SYSTEM Filed Aug. 22; 1938 3 Sheets-Sheet 2 Fig: 4

gg/ 757271 q July 23, 1940. w JAHN 2,208,984

COOLING SYSTEM Filed Aug. 22, 1958 3 Sheets-Sheet 3 o ij Q bb

Patented July 23, 1940 UNITED STATES PATENT orrics COOLING SYSTEM Germany Application August 22,

1938, Serial No. 226,207

In Germany July 17, 1935 11 Claims.

This invention relates to a method of cooling by evaporation and to a system for carrying out this method, more particularly for aircraft motors or engines. The hot cooling agent return- 5 ing from the motor cooling system is evaporated in an evaporator connected, through a pressure Y reducing organ, to the motor cooling system and the vapour or steam is condensed in air-cooled condensers having substantially atmospheric l pressure.

It is already known to remove the heat absorbed by the cooling agent fromthe motor, by evaporating a portion of the cooling agent and condensing the vapour.

In the known evaporation cooling systems evaporation within the cooling chambers of the engine is substantially prevented. To this end the cooling agent leaving the engine cooling chamhers is throttled so as to ensure a higher pres- 30 sure of the cooling agent in the motor. However, the known systems do not ensure a satisfactory operation of the engine under cooling conditions varying over a wide range. Such widely varying conditions occur particularly in 25 aircrafts flying in difierent altitudes and at different speeds. The state of the air, its pressure and, more particularly, its temperature, change with varying altitudes and cause variations in the operation of the condenser. For example, if the 30 condenser is arranged in the wings of an airplane and constructed in such a manner that its cooling surface is formed by the walls of the wing, the plant with a view to its tightness can be operated only at atmospheric pressure. In view of 35 the atmospheric pressure changing with the altitude, the temperature at which the vapour or steam is condensed, will also change.

The condensing conditions are also influenced Ill . by the temperature of the atmospheric air. The

40 lower this temperature is, the more pronounced is the tendency to form a vacuum.

For the rest, the speed of the craft also influences the condensation, the heat conductance through the condenser surface being enhanced with increasing speed.

The known evaporation cooling plants are not suitable to produce always optimum conditions for the operation of the engine under the aforementioned varying conditions because, for inso stance, when the condenser pressure decreases, the pressure at the point where the steam or vapour is developed, that is, in the steam separator or in the engine proper, is also decreased. The decreasing pressure causes decreasing satu- 65 ration temperature of the non-evaporated water returning to the engine. Hence, the engine is cooled more intensively and heat tensions are produced due to this uncontrolled and undesirable increased cooling, whereby the reliable operation of the engine is endangered.

The present invention has for its object to provide various steps and means whereby the cooling agent in the cooling chambers of the engine is controlled to assume a predetermined average temperature.

With this and further objects in view which will be apparent from the following disclosure, I control the fall of pressure between the evaporation vessel or chamber, and the condenser or condensers. The pressure is especially so controlled to maintain a constant average temperature of the cooling agent in the cooling chambers of the engine.

To maintain the said constant average temperature I adjust the pressure difierence between the evaporating vessel and the condenser to maintain a constant pressure in the evaporating vessel.

Further essential features of the invention relate to the provision of stable conditions in the evaporating vessel and in the condenser. Thus, a reliable production and separation of steam-.is efiected in the evaporating vessel which is indispensable in order to ensure a safe control of the. conditions of the cooling agent in the cooling chamber of the engine. Furthermore, condensation surfaces of a sufiicient size are provided and means for rapidly and reliably leading away the condensate and for maintaining a constant heat conductivity of the condenser surface by preventing the formation of an ice skin.

Further features of the invention will be clear from the following detailed description in connection with the accompanying drawings showing by way of example and schematically some embodiments rgf the invention, viz.

Fig. 1 is af iagram of an evaporator cooling system having the invention applied thereto.

Fig. 2 is a longitudinal section, on a larger scale, of an'evap'orating vessel or chamber to be used in connection with the system shown in Fig. 1.

Fig. 3 is a fragmentary section of an evaporating vessel as shown in Fig. 2 but havinga modified control.

Fig. 4 is an axial section of a modified form of an evaporating vessel.

Fig. 5 is a fragmentary view, on a larger scale, of the ring embodying the feeding nozzles according to Fig. 4.

Fig. 6 is a radial section on line VI-VI in. Fig. 5, on a larger scale, through the nozzle ring shown in Fig. 4.

Fig. 6a isa similar section taken on the line VIa-VIa. of Fig. 5.

Fig. 7 is a fragmentary plan view, on a larger scale, of the nozzle ring shown in Fig. 4.

Fig. 8 is a section, on a larger scale, of another modification of the nozzle ring having an adjustable passage cross section.

Fig. 9 is a schematical plan view, on a reduced scale, of the nozzle ring shown in Fig. 8 including a device for adjusting the nozzle cross section.

Fig. 10 is a cross section on line X-X in Fig. 4.

Fig. 11 is a diagrammatic axial section of a further modification of an evaporating vessel including a ring embodying guide blades.

Fig. 12 is a cylindrical section on line XIIXII in Fig. 11, through the ring with the guide blades.

Fig. 13 is a longitudinal section, on a larger scale, of an ejector of the system according to Fig. 1 to draw off the condensate.

Fig. 14 is a fragmentary section of a condenser according to Fig. 1 with a modified arrangement of the exhaust device and Fig. 15 is a diagram of another modification of the evaporation cooling device in which a block cooler is provided additionally to a condenser arranged in the wing of an airplane.

Referring now to the drawings in greater detail, and first to Fig. 1, there is shown a motor or engine i from the cooling chambers of which the hot cooling agent which may be water, is fed through a duct 2, for example, at a pressure of 1.5 kg./cm. or atmospheres gauge and a temperature of 110 0., to a pressure reducing device 3 in which it is reduced, for example, to 0.2 atmosphere and 103 C. In this state it enters the evaporating vessel or chamber 4. The amount of cooling agent remaining liquid after the reduction of pressure is recycled through the duct 5 and by means of the circulation pump 3, to the cooling chambers of the engine while the steam produced by the pressure reduction is delivered to the condenser. Before leaving the evaporating vessel the steam' passes a further pressure regulating device, I, in which it is throttled down to the pressure of the following condenser which corresponds substantially to atmospheric pressure, in such a manner that the pressure in the evaporating vessel 4 is always kept constant. Thus, the steam passes through the outlet regulator I and the duct 8 under the respective atmospheric pressure to the condenser 9. The said condenser takes the form of a condenser arranged in a wing of the airplane in which the engine is accommodated and is of the type having its cooling surface identical with the external wall of the wing, which type is hereinafter referred to as the external wa type of condenser. The steam is advantageously delivered to the nose ID of the wing and prevents the formation of ice at this nose which of course in case of low temperatures would tend at first to the deposition 0 ice.

As the condenser surface is protected against the deposition of ice, a constant and uniform condition of the condenser surface is maintained whereby the condition of the cooling agent, more particularly its average temperature in the cooling chambers of the engine can be governed more reliably. The steam passes from the nose of the wing along the upper and lower inner surface thereof, through channels II and i2, to the rear side and is condensed. The condensate is drawn oif by ejectors l3, l4, l5 from the points which depending on the position of the airplane may form reservoirs for the same. From the ejectors the condensate flows through the ducts l6, l1, l3 to a central point 19 from which it is returned, through the duct 20, to the evaporating vessel 4 where it is mixed with the cooling agent coming from the motor cooling chambers and flowing back to the same. The condensate is cooled down and serves for cooling the oil or other lubricant used in the engine I. To this end it is delivered through the pipe 20 surrounded by cooling ribs 20a, to the lubricant cooler 2| which by means of ducts 22 and 23 is connected with the reservoir for the lubricant of the engine i.

The ejectors l3, l4 and I5 are operated by water under pressure drawn by the central pump 24, from the duct 5 for the cooling agent through the duct 25 which may be provided with cooling ribs as indicated and pressed at a pressure of, for example, 4 kg./cm. gauge (over atmospheric), through the conduit 26 to the distributing point 21 and therefrom through the conduits 28, 23 and 30 to the various ejectors. The central pump 24 is driven by the engine I.

Referring to Fig. 2 which shows an exemplification of a condenser in greater detail, the hot cooling agent entering from .the conduit 2 is delivered to the nozzle-shaped pressure reducing organ 3 in which the difference of the pressure of the entering cooling agent and the pressure of the evaporating vessel 4 is transformed into velocity of flow of the cooling agent.

The diverging jet so produced strikes upon a cup-shaped guiding surface 3| by which it is turned to all sides through about 180. By this change of direction the steam produced by the expansion in the nozzle 3 is separated from the water because the water which is specifically heavier according to the pressure gradient corresponding to the centrifugal acceleration lies against the wall of the guiding-cup 3| in the form of a thin layer while the steam and possibly existing air bubbles remain in the space within the water "balloon thus formed. The water flows through the annular space 32 to the conduit 5, the speed being transformed into pressure.

The steam and air flow through the interior of the evaporating vessel to the regulating organ 1 at the outlet which in the present instance takes the form of a flap valve but may take the form of a slide valve, diaphragm or the like, by way of alternative. By passage through the throttle organ 1 the steam pressure as mentioned is reduced from the pressure of the vessel 4 to the pressure of the condenser 3 which corresponds approximately to the pressure of the atmosphere.

The throttle organ I is adjusted by the control member'33, through rods and levers 34, 35. The control member 33 comprises a bellows containing a predetermined amount of air and acted upon by the pressure in the evaporating vessel 4. When this pressure rises, the bellows is compressed and increases the passage cross section offered to the steam by the flap valve I. In the opposite case, for example, when in great altitudes the condenser pressure falls and as a result the pressure in the evaporating vessel 4 decreases, the bellows 33 expands and tends to close the flap. Thus further fall of the pressure in the vessel 4 is prevented.

The bellows 33 of course responds also to changes of pressure in the evaporating vessel caused by changes of the motor output. For example, if the pilot suddenly opens the throttle causing a larger production of vapour and thus an increasing pressure in the evaporating vessel, the bellows 33 is compressed and opens the flap valve 1. As a result, the increased pressure is compensated by a larger amount of steam flowing to the condenser.

It will be understood that as the bellows 33 is very sensitive and causes large strokes, relatively small variations of pressure in the evaporating vessel 4 are sufiicient to produce the required control movements of the flap valve '7. Hence, the pressure in the vessel 4 remains practically unchanged.

The constancy of the pressure in the evaporating vessel with variable conditions in the condenser is the fundamental condition for the constancy of the average temperature of the cooling agent in the motor cooling chambers.

By way of alternative, the control for the flap valve I may be acted upon by atmospheric pressure instead of being acted upon by the pressure in the vessel, as in Fig. 2. An arrangement of this type is shown in Fig. 3 and is differentiated from the arrangement shown in Fig. 2 merely by the position of the bellows which in this case is arranged in a space communicating with the space below or behind the flap valve l which has the same pressure as the condenser 9.

The arrangement shown in Fig. 3 operates in such a manner that when the atmospheric pressure drops and the condenser pressure is reduced, for example, because the airplane rises, the diaphragm 33 expands and the flap valve i, which is mounted to turn about centrally located pivots indicated by dotted lines is turned in a direction to close the conduit 8. Of course, also in this case slide valves, diaphragms or the like provided with suitable transmission members to the bellows 33 may be used instead of a flap valve. It will be understood that a control organ directly acted upon by the atmospheric pressure, as shown in Fig. 3, ofiers the advantage of acting more promptly since the atmospheric pressure generally is the primary variable factor on which the pressure in the evaporating vessel depends.

By way of alternative. control organs acted upon by temperature may be used for the throttle valve i instead of control organs acted upon by pressure. For example, a thermostat controlled by the temperature in the evaporatingvessel it may be used at 33, the expansions and contractions of which by temperature variations are transmitted to the throttle organ.

According to Fig. 2, the passage cross section of the nozzle 3 in which the pressure difierence between the motor cooling chambers and the evaporating chamber 4 is converted into speed, is adjustable by means of a movable hollow needle 38 acted upon by a bellows 3B which is secured at one end to the feeding pipe 2 and at the opposite end to the hollow needle 38. The space within the bellows 39 communicates, through apertures 39', with the pipe 2 and thus is acted upon by the pressure of the cooling agent in the motor cooling chambers. When the pressure in the motor cooling chambers decreases, the bellows 39 is compressed and thus raises the hollow needle 38 so that the annular passage cross section of the nozzle 3 is decreased. In this manner the output of the engine becomes a controlling factor in the adjustment of the average temperature of the cooling agent in the motor cooling chambers. The hollow needle 38 at the same time feeds the condensate delivered through the conduit 20 from the condenser 8 and is formed with a nozzle-shaped end 49. The nozzl 3 together with the hollow needle 36 acts like an ejector, the hot cooling agent fed through duct 2 and the condensate fed through needle 38 producing a mutual suction efiect, depending on the relative pressures. The arrangement shown offers the advantage that the condensate is also subjected to the separator effect produced in the guide cup 35. Therefore, no air can enter from the condensate into the motor cooling system but the air is separated from the water and returned, together with the iii steam, to the condenser from which it is blown oil to the atmosphere through a vent opening which will be described later.

Referring now to Figs. 4 to- 10, there is shown another form of the evaporating chamber provided with a larger number of small nozzles arranged in turbine-fashion on a ring M, instead of one larger. centrally positioned nozzle 3. As shown in Fig. 5, the ring is formed with milled or out slots 52 the upper edge 43 of which is rounded so as to prevent whirls. The slots 42 together with the surrounding upper portion of the cover 441 of the evaporating chamber form the individual nozzles which together have the same effect as the large nozzle 3 and the guiding cup at according to Fig. 2. In the evaporating chamber according to Fig. 4 the liquid is also driven against the outer walls of the evaporating chamber in the form of a thin layer so that steam and air are collected in the center of the liquid balloon" and allowed to flow off in upward direction through the pipe 45, as indicated by the arrows. The hot cooling agent coming'from the motor cooling chambers is delivered to the nozzles through a casing it which in the present instance is spirally shaped as shown ln Fig. 9.

The nozzle ring M is formed with a sharp end edge 45'! wherebyv drops of water are prevented from being thrown into the interior space. Moreover, a mantle-shaped screen member 48 is arranged in the upper part of the evaporating vessel to protect the flowing off steam against spray water.

The separating efiect between the liquid and evaporated portions of the cooling agent will be clear from Fig. 7 in which the arrows '49 indicate the direction of the jets from the nozzles, that is, the tangential component of the speed of the jet. This tangential movement is turned by the cylindrical cover of the separator in a centripetal direction, whereby a pressure gradient corresponding to the centrifugal acceleration is formed (u=circumferential speed, r=radius of the cylindrical cover) which causes the separation according to the specific weight.

In order to make the nozzle cross section variable, as in Fig. 2, a divided nozzle ring may be provided, as shown in Fig. 8. The lower portion 50 of this ring is fixedly mounted in the.

would give the same result.

iii) In order to turn the upper ring part automatically with respect to the lower part, a control device 52 is provided as shown in Fig. 9 with its axis tangentially to the spiral casing 46. This control device may also consist of a bellows acted upon by the pressure of the cooling agent in the motor cooling chambers.

The nozzle 42 apart from the separating effect twists the liquid from which the steam has been separated, whereby it is possible to deliver the liquid to a lower spiral casing 58 as shown in Fig. 10, and to regain its pressure.

In order to prevent excessive rise or the steam pressure in the evaporating vessel in case of a sudden considerable increase of output of the engine, a safety-blow-ofi valve or is provided in the steam collecting chamber iii of this vessel. The blown ofi steam is advantageously led, through a conduit to, into the exhaust piping or to the vicinity thereof to render it invisible.

In a similar manner as with the evaporating chamber according to Fig. 2, the condensate may be fed into the evaporating chamber shown in Figs. 4- in such a manner that the cooling agent coming from the motor cooling chambers and the condensate act upon each other in an electorfashlon. To this end, additional slots did may be provided between the slots 522 of the nozzle ring ti which, for example, are connected by radial channels tic to an annular conduit use forming the terminal of the return duct a for the condensate.

An essential feature or the evaporating chamber shown in Fig. =3 resides in the fact that it can be made in a compact and light construction, for example, of thin light metal sheets. The nozzles in the ring it are likewise easy to produce.

Referring to Fig. .11, there is shown a steam separator connected with the store tank. The liquid cooling agent rotating within the cylindrical walls of the upper portion sr after passage through inlet nozzles of a ring iii formed as in Fig. 4 is turned at an angle to the axial direction by means of annularly arranged guide blades 558 as shown in Fig. 12. The blades are so formed in connection with a centrally arranged downwardly reduced body did that the cross section is gradually increased and a certain amount oi pressure regained.

The steam separators described have the common feature. that the produced steam is reliably separated in a small space. Thus, steam bubbles possibly contained in the liquid cooling agent are prevented irom returning to the motor cooling chambers and from fiusing non-uniform heat transmissions in the engine and uncontrollable conditions. It would not be possible otherwise to maintain a predetermined average temperature in the motor cooling chambers.

Referring to Fig. 13, there is shown one of the electors l3, l4, I! which as hereinabove mentioned are fed with water under pressure by the central pumps 24 and serve to draw oil the condensate produced in the condenser 9, on a larger scale. The water under pressure coming from the central pump 24 enters, for example, under a pressure of 4 atmospheres, through the central bore of the part 5! and in view of the nozzle effect of the part 60, draws on the condensate from the spaces SI and 62 into the diiIusorshaped part 63 in which the dynamic energy is again transformed into pressure. The mixture of water under pressure and condensate leaves the ejector at the end 64 and flows through one of the conduits i6, ii, 88 and the central connection point is to the condensate return conduit 2d.

The ejectors which according to the position of the aircraft are not immersed in the condensate act as jet condensers or air pumps. The electors should be formed with nozzles of such a shape that cavitation phenomena are absolutely prevented. The nozzles are shaped so that the jet of the mixture is first contracted until the condensation is finished.

The circulating system from the central pump it through the ejectors to the central pipe 20 as far as it is positioned in the wing, is constructed as a welded conduit or as a conduit with reliable joints of another suitable type and does not require any attendance as movable parts are avo ded.

In View of the small amount of condensate, compared to the total amount of cooling agent circulating in the system the energy required for driving the central pump it is so small that also the electors not immersed in the condensate in order to ensure a reliable control of the temperature of the cooling agent remain always in operation.

The reliable operation of the condenser a according to Fig. 1 is enhanced by a suitable arrangement of the vent pipe 5b in such a manner that the lower end as of this pipe extends into the condenser to such an extent that the vent pipe will not be immersed in the water at any position of the airplane, more particularly at vertical or nearly vertical flying position.

A modification of the vent device is shown in Fig. 1a. In this case the parts hi and 5d of the vent device are arranged so that air and excesrive steam how in the same direction as the condensate.

Fig. 15 shows a modification of the evaporating cooling system according to the invention for plants where in view of the large output of the engine an external wall condenser of the required size cannot m accommodated in the wings so that one or more additional condensers are required.

it is then essential at which point these additional condensers are arranged with respect to the steam throttle point i which is arranged before the external wall condensers and reduces the pressure of the steam separator to that of the external wall condenser.

The additional condenser its in Fig. 15 is of the block type and arranged before the throttle point i.

The said block type condenser consists of vertical tubes it provided with cooling ribs H; The steam enters the tubes at the top and the condensate is drawn oiif at the bottom through the ejector II. The block cooler is mounted at the body and cooled by the air passing in the direction of the arrow II.

The cooling agent circulates in the plant according to Fig. 15 as follows:

The cooling agent flows from the cooling chambers of the engine I through pipe 2 to the steam separator 4 from which the liquid cooling agent is returned through pipe 5, by the circulation pumps 6, to the motor cooling chambers, while the steam occurring in the steam separator is at first guided, through conduit 8, to the additional condenser G9 in which a part of the steam is condensed. The rest of the steam passes through a pipe 14 to the throttle point I and is throttled,

down to the pressure of the external wall condenser. Furthermore, the steam flows through aaoaeea conduit Ba to the external wall condenser 9, as in Fig, 1, to the nose of the wing. The condensate is drawn off through the ejector l9 and flows through conduit 20 to the reservoir '15 into which the condensate drawn off by the ejector '12 of the additional condenser 69 is also moved through aduct 16. In this reservoir the condensates coming' from the various spaces with difierent pressure levels are allowed to expand and mixed so that they get in a uniform condition to the pumps 11 through which they are recycled to the main pipe 5 for the cooling agent.

In Fig. 15 only a part of the inner equipment of the condenser 9 has been shown and it may be completed in the same manner as in Figs. 1 to 14. For example, besides the ejector is further ejectors may be arranged at other places of the condenser.

The additional condenser (it normally operates at the pressure of the steam separator A, .that is to say, at a pressure above atmospheric and above that of the condenser 9.

At high altitudes, the output of the additional condenser is increased due to the pressure being kept constant in the steam separator 4. Of

course, the additional condenser in this case is subjected to increased pressure (in an altitude of 10,000 m.:0.75 atm., At being=l60). Now, if for any reasons it becomes leaky, it must be prevented from becoming entirely inoperative, whereby the whole cooling system would be endangered. For this purpose a device is provided by means of which the additional cond nser 0% can be fed alternatively with high or low pressure steam, high pressure steam being the steam under the pressure of the steam separator 4 and "low pressure steam being steam under the pressure of the external wall condenser E.

This device comprises an additional throttle valve I0 arranged before the additional condenser and coupled with the throttling organ i.

To this end the throttle valve 18 is hingedly connected, by means of a rod 19, to a lever 8t pivoted at 8!. The extreme end of this lever is acted upon by a rod 82, connected to hell crank lever 83 and to the angle lever 84 which by means of a rod' B5 acts upon the rod system 34, 35 of the throttle valve l. By depression oi. lever 83 the throttle valve i is opened entirely and the valve 18 is displaced in a left hand direction in such a manner that it throttles the passage of the steam coming from the separator 4 through pipe 8.

Accordingly in case of this adjustment of the system the throttling action is exerted by the valve 18 rather than by the flap valve 7 and the pressure prevailing in the additional condenser 69 is the same condition as that of the external condenser 9. Of course, in this case the temperature level of the cooling system is reduced. However, the system becomes by no means inoperative, as the additional condenser becomes entirely ineffective only when its condensator reservoir is destroyed. Hence, the airplane can continue its flight, although at a reduced output, for a long time.

By way of alternative, the switching from throttle organ 1 to throttle organ 18 may be carried out automatically by means of a pressure feeling member 86, comprising a bellows the inner space of which communicates with the lower part of pipe 8 and which is connected to one end of the lever 80. When the pressure in the lower part of pipe 8 is decreased, the bellows is compressed against action of a spring 81 and swings the lever 81! in the same direction as by depression of lever 83, namely, in such a manner that the throttle valve 18 is moved into the duct 8 and reduces the cross section thereof. In this case the steam flows partly to the additional condenser and partly directly through pipe 8a to the external wall condenser 9.

Normally the throttle organ 1 is acted upon by the pressure regulator 33 in the same manner as in Figs. 1 and 2. For example, in this normal case, the hot cooling agent is supplied to the steam separator 4 at a pressure of 4 atmospheres absolute pressure and 120 C. where it is reduced to 2 atmospheres absolute pressure and 110 C. In this condition the liquid condensate passes through the duct 5 back to the motor cooling chambers while the vapour or steam passes through theadditional condenser 69 to the throttle point I where it is throttled down to 1 atmosphere absolute pressure and C.

In order to avoid a stufllng box at the point where the rod 19 enters the pipe 8, a bellows I9 has been provided which, however, has no controlling function.

Referring again to Fig. 2, it will be seen that, as an alternative to the pressure control organ 33, 3d, a thermostatic device 33', 34' has been shown by dot and dash lines. The said thermostatic device comprises an expansion rod 33' fixedly secured with its left hand end to the wall of pipe 8 and formed with a slotted end portion 3d at its right hand and engaged by a projection 35' of rod 35. It will be understood that any rise of temperature of the cooling agent in the pipe 8 due to increasing pressure will cause expansion of rod 33' and movement of the flap I in the opening direction. Of course, the arrangement has been shown purely schematically and it will be necessary to provide other lever arm ratios in order to obtain sufiicient strokes with respect to the flap valve movements.

I am aware that many changes may be made and numerous details of construction may be varied through a wide range without departing from the principles of this invention and I, therefore, do not purpose limiting the patent granted hereon otherwise than is necessitated by the prior art. g

It will be clear that the various control organs of my cooling system maybe so constructed and adjusted as to meet with the above-mentioned conditions. More particularly, the control organ controlling the pressure diflference between the evaporating chamber and the condenser under atmospheric pressure is provided to adjust a predetermined average temperature of the cooling agent in the engine cooling chamber as a function of the varying cooling conditions, especially in such a manner that the said temperature is kept constant with varying cooling conditions, the

variations of which may be due, for example, to changing temperature, pressure or velocity of the atmospheric air acting upon the cooling system. In most instances this may be realized by adjusting the pressure in the evaporating chamunder atmospheric pressure connected to the evaporating chamber, a conduit for refeeding the condensate into the cooling circuit, a throttle organ controlling the pressure of the vapourdischarged from the evaporating chamber and a control for said throttle organ influenced by the pressure in the evaporating chamber.

2. In a system for recooling the cooling agent of an internal combustion engine, an evaporating chamber, a conduit feeding said cooling agent from the engine cooling chamber to said evaporating chamber, a pressure reducing organ in said conduit, a conduit for refeeding the nonevaporated cooling agent to said engine cooling chamber, an air-cooled condenser substantially under atmospheric pressure connected to the evaporating chamber, a conduit for refeecling the condensate into the cooling circuit, a throttle organ controlling the pressure of the vapour discharged from the evaporating chamber and a thermostat acted upon by the temperature in the evaporating chamber and controlling said throttle organ.

3. In a system for recooling the cooling agent of an internal combustion engine, an evaporating chamber, a conduit feeding said cooling agent from the engine cooling chamber to said evaporating chamber, a pressure reducing organ in said conduit, a conduit for refeeding the nonevaporated cooling agent to said engine cooling chamber, anair-cooled condenserconnected to the evaporating chamber, a conduit for refeeding the condensate into the cooling circuit, a throttle organ controlling the pressure of the vapour discharged from the evaporating chamber and a control for said throttle organ influenced by the atmospheric pressure.

4. In a system for recooling the cooling agent of an internal combustion engine, an evaporating chamber, a conduit feeding said cooling agent from the engine cooling chamber to said evaporating chamber, a pressure reducing organ in said conduit in the form of a nozzle, a vapourseparator comprising an arched guiding surface adapted to change the direction of the jet of said nozzle and to form a hollow balloon of the separated liquid at the walls of said surface, a conduit for refeeding the non-evaporated cooling agent to said engine cooling chamber, an aircooled condenser connected to the evaporating chamber, a conduit for refeeding the condensate into the cooling circuit, a throttle organ controlling the pressure of the vapour dis-charged from the evaporating chamber and a control for said throttle organ influenced by the condition of the vapour in the evaporating chamber.

5. In a system for recooling the cooling agent of an internal combustion engine, an evaporating chamber, a conduit feeding said cooling agent from the engine cooling chamber to said evaporating chamber, a pressure reducing organ in said conduit in the form of a nozzle comprising means for adjusting the passage cross section of said nozzle as a function of the pressure of the cooling agent in the engine cooling chambers, a. vapour separator comprising an arched guiding surface adapted to change the direction of the jet of said nozzle and to form a hollow balloon of the separated liquid at the walls of said surface, a conduit for refeeding the non-evaporated cooling agent to said engine cooling chamber, an aircooled condenser substantially under atmospheric pressure connected to the evaporating chamber, a conduit for refeeding the condensate into the cooling circuit, a throttle organ controlling the pressure of the vapour discharged from the evapcrating chamber and a control for said throttle organ influenced by the condition of the vapour in the evaporating chamber.

6. In a system for recooling the cooling agent of an internal combustion engine, an evaporating chamber, a conduit feeding said cooling agent from the engine cooling chamber to said evaporating chamber, a pressure reducing organ in said conduit in the form of a nozzle, comprising a hollow needle adapted to feed the condensate and to cause, in connection with the nozzle, mutual ejector efiects of the condensate and the cooling agent coming from the engine cooling chambers, a vapour separator comprising an arched guiding surface adapted to change the 7. In a system for recooling the cooling agent of an internal combustion engine, an evaporating chamber, a conduit fg said cooling a ent from the engine cooling chamber to said even-- crating chamber, a pressure reducing organ in said conduit comprising two superposed nozzle rings which are relatively turnable and formed each with a plurality of'nozzle portions adapted to be turned into any relative position of non-register, partial register and perfect register, a com duit for refeeding the non-evaporated cooling agent to said engine cooling chamber, an aircooied condenser connected to the evaporating chbe a conduit for refeeding the condensate into the cooling circuit, a throttle organ control ling the pressure of the vapour discharged from the evaporating chamber and a control for said throttle organ influenced by the condition of the vapour in the evaporating chamber.

8. In a system for recoolingthe cooling agent of an internal combustion engine, an evaporating her, a conduit feeding said cooling agent from the engine cooling chamber to said evapcrating chamber, a pressure reducing organ in said conduit comprising two superposed nozzle rings which are relatively turnable and formed each with a plurality of nozzle portions adapted to be turned into any relative position of nonregister, partial register and perfect register, means for controlling the relative position of said two rings automatically depending on the pressure of the cooling agent in the engine cooling chambers, a conduit for refeeding the nonevaporated cooling agent to said engine cooling chamber, an air-cooled condenser connected to the evaporating chamber, a conduit for refeeding the condensate into the cooling circuit, a throttle organ controlling the .pressure of the vapour discharged from the evaporating chamber bit (iii

anda control for said throttle organ influenced crating chamber, a pressure reducing organ in said conduit, a conduit for refeeding the nonevaporated cooling agent to said engine cooling chamber, an air-cooled condenser under substantially atmospheric pressure connected to the evaporating chamber, a conduit for refeeding the condensate into the cooling circuit, a pressure control organ for the vapour flowing from said evaporating chamber to said condenser, at least one additional condenser normally under higher than atmospheric pressure between said evaporating chamber and said pressure control organ, a second pressure control organ between said additional condenser and said evaporating chamber, and means operatively connecting said first and second pressure control organ and adapted to hold said second pressure control organ normally in inoperative condition and to move said second pressure control organ into operative condition and said first pressure control organ into inoperative condition when the pressure in said additional condenser falls below its normal pressure.

10. In a system for recooling the cooling agent of an internal combustion engine, an evaporating chamber, a conduit feeding said cooling agent from the engine chamber to said evaporating chamber, a pressure reducing organ in said conduit, a conduit for refeeding the non-evaporated cooling agent to said engine cooling chamber, an air-cooled condenser under substantially atmospheric prassure connected to the evaporating chamber, a conduit for refeeding the condensate into the cooling circuit, a pressure control organ for the vapour flowing from said evaporating chamber to said condenser, at least one additional condenser normally under higher than atmospheric pressure between said evaporating chamber and said pressure control organ, a second pressure control organ between said additional condenser and said evaporating'chamber, and automatic means comprising a pressure feeler and adapted to hold said second pressure control organ normally in inoperative condition and to move said second pressure control organ into operative condition and said first pressure control organ into inoperative condition when the pressure in said additional condenser falls below its normal pressure.

11. In a system for recooling the cooling agent of an internal combustion engine for aircraft, an evaporating and steam separating chamber, a conduit for feeding the cooling agent from the engine cooling chamber to the evaporating and steam separating chamber, pressure reducing means associated with said conduit for reducing the pressure of the cooling agent so that this cooling agent is maintained in a liquid state in front of said means and is partly' vaporized behind said means, guide plates in the steam separating chamber arranged to deflect the cooling agent coming from the pressure reducing means so as to spread the agent in a thin film which permits a free discharge of the steam, a circulating pump connected to the engine cooling the steam separating chamber in dependence upon the engine output, a plurality of jet pumps for returning the condensate of the cooling agent arranged at one of the main collecting points of the condensate in the condenser and said collecting points being formed in the various main flying positions.

FRIEDRICH W. JAHN. 

